Sam’s least favorite part of her afterschool job at the supermarket is closing. When closing the store, the break room has to be swept and mopped. Each of the students who work at the store part-time take turns closing, and every Friday night is Sam’s turn. On Friday, Sam got her mop and broom and headed up to the break room. It seemed to be even messier than usual. “Oh no, I will never get done,” Sam sighed, but she picked up the broom and began to sweep.

In just fifteen minutes, Sam had swept four-fifths of the room. She was amazed at how quickly the task was getting done with a little focus and effort.

How could we write this fraction as a decimal?

How could we write the fraction of the room left to clean as a decimal?

Guidance

You will recall that to do this, we drop the % sign and move the decimal point two places in to the left. These two places represent the hundredths place of the decimal.

becomes

Our answer is
.

We can also write a decimal as a percent. To do this, we are going to move the decimal point two places to the right and add a percent sign.

Write
as a percent.

To do this, we move the decimal point two places to the right because two decimal places represent hundredths and percents are out of 100. Then we add in the % sign.

Sometimes, you will have a decimal that is written with a zero for the tenths place. We do the same thing to convert to a percent. Move the decimal two places to the right and add a percent sign.

Write
as a percent.

becomes

What about a decimal that does not have two decimal places represented?

Write
as a percent.

To do this, we move the decimal point two places to the right, which will require adding a zero. Then we can see that two tenths becomes 20 percent.

What about if you have a decimal with more than two places?

When this happens, it is an interesting case, because you have to move the decimal point two places to the right, but you will have a percent that is also a decimal.

becomes
.

Now it is time for you to practice. Write each decimal as a percent.

Example A

Solution:

Example B

Solution:

Example C

Solution:

Now let's go back to Sam and her sweeping. Here is the original problem.

Sam’s least favorite part of her after school job at the supermarket is closing. When closing the store, the break room has to be swept and mopped. Each of the students who work at the store part-time take turns closing, and every Friday night is Sam’s turn. On Friday, Sam got her mop and broom and headed up to the break room. It seemed to be even messier than usual.

“Oh no, I will never get done,” Sam sighed, but she picked up the broom and began to sweep.

In just fifteen minutes, Sam had swept four-fifths of the room. She was amazed at how quickly the task was getting done with a little focus and effort.

How could we write this fraction as a decimal?

How could we write the fraction of the room left to clean as a decimal?

Sam had swept four - fifths of the room. We can convert four - fifths to a decimal. First, let's write it as a proportion.

Now we can solve the proportion.

The decimal is
.

Now we can use mental math to figure out the decimal of the room that she has left to sweep.

Sam has
left to sweep.

Vocabulary

Here are the vocabulary words in this Concept.

Percent

is "per-cent" or "per-hundred", it is a quantity written with a % sign, a part of a whole (100)

Fraction

a part of a whole, related to decimals and percents.

Decimal

a part of a whole shown by a decimal point, hundredths means two decimal places.

Equivalent

means equal

Guided Practice

Here is one for you to try on your own.

What is
as a percent?

Answer

To convert a decimal to a percent, we move the decimal point two places to the right and add a percent sign.